Items with '#[macro_use]' not inlined by 'inline_attribute_width' config option

[TrinityCoder]

1. Description

No matter the value set in the option inline_attribute_width (100, same as max_width for me), rustfmt never inlines this:

#[macro_use]
extern crate static_assertions;

into this:

#[macro_use] extern crate static_assertions;

However, when I change the first code snippet into this:

#[cfg(abc)] extern crate static_assertions;

it suddenly works. According to the Rust docs, macro_use is one of many built-in attributes, just like cfg is an attribute. Therefore I came to conclusion, that rustfmt should inline the first case as well.

2. Attempt to a solution

I think this issue has something to do with the pull request #2412, which was created because rustfmt was in some cases incorrectly reordering items having the macro_use attribute (see #2399 for example). The pull request fixed the reordering problem, but the price for it was that since then, rustfmt ignores the macro_use attribute to the point that it does not inline it when it should.

I see the source code of rustfmt for the first time today and I am not yet much familiar with it, but I have figured out that if in the file src/reorder.rs:178 the contains_macro_use_attr function gets changed to always return false

fn contains_macro_use_attr(item: &ast::Item) -> bool {
    //attr::contains_name(&filter_inline_attrs(&item.attrs, item.span()), "macro_use")
    false
}

and rustfmt gets recompiled, it suddenly starts to properly inline the macro_use attribute.